MagnaCut Oil Quench Testing

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Feb 15, 2016
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.182" thick samples:

Stress Relief - 1300F for 2 hours, oven cooled overnight

Max ramp speed to 1600F, placed knives in oven at 1200F (so the blade coating properly bakes.), held at 1600 for 30 minutes for preheat.

Max ramp to 2050F, held 20 minutes, quenched in oil, interrupting at 1000F. Oil was175F

Air cool to (near) room temperature, then soaked in LN2 for 60 minutes.

2 hour temper at 300F, quenched in water, then soaked in LN2 for another 60 minutes

2 hour temper at 350F


I did this process with 2 samples, plus 2 others I plate quenched with compressed air to compare. The oil I used was Citgo Quenchol 521, a medium speed oil. In my testing, it took about 14 seconds to get down to 1000F.

To get as accurate as possible with my 1000F timing, I used a few samples to gauge their glow in the dark, and then quenched them until I had the timing down.

I used Condursal Z1100 compound for the oil quenching (Though I steel foil wrapped them for the stress relief.), and of course steel foil wrapped the plate quench samples.

My results with the Condursal were sadly disappointing, and there was a good deal of decarb.

The hardness on the plate quenched samples were 61.5-63RC, testing multiple times on each sample in multiple locations. The oil quenched samples were 61.5-64RC, so pretty much equal. Unfortunately, because the decarb was so bad, I am going to call it a failure. The anit-scale compound is rated at 2013F max temp, so it just didn't hold up.

I am going to do another round of tests to determine how quickly it will quench if in a steel foil pouch (Instead of using anti-scale compound).
 
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Why declare the decarb ones a failure? Did you or will you grind off the decarb? How do you know how bad it is?

14 seconds seems like a long time for the blade to reach 1000F
 
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Why declare the decarb ones a failure? Did you or will you grind off the decarb? How do you know how bad it is?

14 seconds seems like a long time for the blade to reach 1000F
It's a failure in that the hassle of removing that much decarb makes plate quenching more desirable to me.

And yes, I was surprised with how long it took to get to 1000F. With thinner stock quenching from 1950F, I usually have a much faster quench. Granted, the slower quench at least makes it much easier to not quench it past 1000 degrees.

I will likely try a faster oil in my next test. In the past I had good results quenching 3v in steel foil and a faster oil. This Citgo oil is fairly new to me.
 

Stacy E. Apelt - Bladesmith

ilmarinen - MODERATOR
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I'm curious why the second cryo and why different temperatures for the two tempers?

I would not try to catch the cooling at exactly 1000°F. Just quench until black and air cool to ambient, then cryo.

Did you grind away all decarb before using the hardness tester? Decarb cab skew the test results a good bit.

Here is Larrin's test results and recommendation:
"Magnaquench heat treatment is 2050°F austenitize (20 minutes), plate/oil quench, and 2×2 hour 350°F temper. The hardness is somewhat higher if a cryo step is added after the quench".
 
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I'm curious why the second cryo and why different temperatures for the two tempers?

I would not try to catch the cooling at exactly 1000°F. Just quench until black and air cool to ambient, then cryo.

Did you grind away all decarb before using the hardness tester? Decarb cab skew the test results a good bit.

Here is Larrin's test results and recommendation:
"Magnaquench heat treatment is 2050°F austenitize (20 minutes), plate/oil quench, and 2×2 hour 350°F temper. The hardness is somewhat higher if a cryo step is added after the quench".

The low temp first temper is Roman Landes' recipe. To quote what he said: "The first temper is a low temper so the remaining RA is stabilized at the lowest level possible and at the same time there is enough stress relief in the martensite that has been built and furthermore the transformation from tetragonal to cubic martensite is started. The water quench speeds the whole thing up and avoids precipitation of embrittling phases."

In my testing, the steel loses its glow completely in the dark at 900F (I did this test by having steel sit in the oven at specific temps and pulling them out in the dark.). My goal is usually to hit black, but I worry more about quenching it too long than too little, since it goes on plates after the oil, anyways. Gauging where it's at temp wise once it's black is tough, whereas with some glow I know exactly where it is based on my testing at various temps.

As for the decarb, I ground material off, took a reading, ground more off, took a reading, and so on, until the hardness readings stopped increasing. And of course I liquid cooled it so as to not ruin the temper.
 
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I appreciate your write up here and contributing to the knowledge base.
I’m curious, are you a fulltime maker or hobbyist? What kind of blades are you making and how many?
I get the desire to grind wear resistant steel pre hardening, I’m all for this.
 
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I'm just a hobbyist, which is probably why I have the time to do all this testing. I also can't make a lot of knives anymore due to health reasons (Maybe I'll get a CNC mill someday!).

I make all kinds of knives, but mostly 3-6 inch stuff. Lately I have been making puukkos, generally scandi or saber grind. I also make hunting, bushcrafting, and camp knives. I've been getting into making kitchen knives, which is what has gotten me so motivated to test all this oil quenching, because doing a full flat grind on a kitchen knife post heat treat is a huge pain!!

I used to oil quench a lot with 3v, and had good success with Roman Landes' recipe. It's also why I am a bit stubborn about it, because no matter what anyone tries to tell me, I can't help but trust the words of Landes.

Ultimately I have been very frustrated over the years with all the lack of information on oil quenching air hardening steels, and have been able to find almost no information on any testing. So I finally decided the only way I'd get the information I want, is by testing myself.
 

bluntcut

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I just measured(infrared) ~800F after 10 seconds plate quench .180" thick chopper blade from 2050F aust. Similarly ~650F after 6 seconds for .156" thick.

Idea behind oil quenching is to quickly cool (below 1000F) to minimize carbide precip and other transformations. Measured temp w/o foil as 760F (so probably it is 800F in foil prior to removal). Stating the obvious ... your 14 seconds int oil quench is slower than int plate quench with blade still in ss foil. Coating is a good insulator to quenchant (brine included), it make sense to use ss foil instead of refract coating. You can remove foil then int oil quench. I found quench with foil is sort of messy and beside removing foil first doesn't cool blade down that much.
 
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I remember that you are doing this to save grinding hard steel. It sounds like it wouldn't work for you but on things like kitchen knives with no plunge it is possible to grind the full blank with a taper so that you can still plate quench after. @Willie78 hardened some blade like that for me. One in M4 and the other in S35VN. The M4 one was around 0.007 at the edge and there were now problems.
 
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I have ground the bevels on quite a few stainless steel blades prior to HT and used plates/forced air with excellent results. I am amazed at just how quickly the area close to the edge goes to black because it's so thin.....seconds, not minutes. While I just simply lay the blade onto a plate, and then clamp the other plate on top, there is a way to use plates and get good contact on both sides. Forgive my feeble attempt at making an image!

platequench.jpg
 

Hubert S.

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I have ground the bevels on quite a few stainless steel blades prior to HT and used plates/forced air with excellent results. I am amazed at just how quickly the area close to the edge goes to black because it's so thin.....seconds, not minutes. While I just simply lay the blade onto a plate, and then clamp the other plate on top, there is a way to use plates and get good contact on both sides. Forgive my feeble attempt at making an image!

View attachment 1577540
I use a woodworking vise with a piece of rubber between the upper quench plate and the vise jaw to allow for some give. I think I first saw this arrangement in a post by JTknives JTknives and pretty much just copied it. I've never tried to quench a blade with already ground bevels, but I think it might work ok with some geometries.
 
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That's pretty interesting. My plate quenching system is not exactly complex. I just set one plate on the other and press down on it by hand while blowing air between them. If oil quenching turns out to be inferior in the end, I'll probably have to improve my plate quenching system a bit! :D

I ordered some Parks 50 and will try again later this week once it arrives.
 
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Aging thread but I am very interested in this subject. If you’re still around, Mobius, I’d like to know how it went went with the Parks 50.
 
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Too fast quenching rate will result in unnessary stress = lower toughness. Magnacut has good amount of Mo so it will harden close to maximum hardness even with still air cooling.
 

Signalprick

Jason Ritchie - Ritchie Handmade Knives
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It seems like those hardness readings are a little odd? Maybe not but from 61.5 - 63, 64? I can see a half point or even a full point difference through the blade but is that much difference normal?
 
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